This invention relates to an apparatus for transversely centering long cylindrical objects such as cast iron pipes as they are rolled through a furnace in a direction perpendicular to their axes in order to heat them or to impart some other form of heat treatment.
Besides the usual heating means, a furnace of this type includes a bed provided with tracks or rails, generally parallel to each other and to the longitudinal axis of the furnace, over which the pipes are rolled by a conveyor from the upstream furnace entrance to the downstream furnace exit.
The pipes may be drawn downstream through the furnace by toothed chains parallel to the rails, with the teeth protruding above the rolling surface of the rails so as to tangentially contact the outer surface of the pipes (similar to a car wash conveyor). Two parallel chains may be provided, with one located under each end of the pipes. In the longitudinal plane of the furnace, the space between adjacent te is set to accommodate a large range of pipe diameters. In the transverse plane, the chain teeth are aligned perpendicular to the path traveled by the pipes.
The movement of the chains, which are drawn by known means, is synchronized so that the pipes will roll transversely over the rails, with their axes orthogonal to the longitudinal axis of the furnace.
Any unwanted axial slippage of the pipes toward one of the lateral walls of the furnace is periodically corrected by movable centering stops placed on either side of the walls. The movement of these stops is synchronized, and they exert force upon the ends of the pipes along their longitudinal axes.
The movable stops are activated by control means such as linear actuators mounted outside the furnace perpendicular to its lateral walls. Thus arranged, the stops maintain the pipes in the center of the furnace and thus prevent friction and any unwanted catching of the ends of the pipes on the inner walls of the furnace.
Positioning means such as these have the disadvantage, however, of being bulky and of blocking access to the furnace. Furthermore, the longitudinal sliding needed to reposition the pipes, as described above, affects the alignment of the movable stops by wearing away the crown of the rails by abrasion, which necessitates their regular and frequent replacement with all of the material and financial drawbacks that this entails.